modules about image filters pros and cons

@halavaty@hossain
It would be great to have a module that compares the pros and cons of popular filters, e.g., such as:

Gaussian Blur

Median Filter

Maybe we should restrict ourselves to maximally comparing three (better only two) filters per module. To compare other filters we could make a new module. This would keep it nicely modular and at the same time not overload the students with information.